Papillomaviruses are small DNA tumour viruses, which are highly species specific. So far, over 100 individual human papillomavirus (HPV) genotypes have been described. HPVs are generally specific either for the skin (e.g. HPV-1 and -2) or mucosal surfaces (e.g. HPV-6 and -11) and usually cause benign tumours (warts) that persist for several months or years. Such benign tumours may be distressing for the individuals concerned but tend not to be life threatening, with a few exceptions.
Some HPVs are also associated with cancers, known as oncogenic HPV types. The strongest positive association between an HPV and human cancer is that which exists between HPV-16 and HPV-18 and cervical carcinoma. Cervical cancer is the most common malignancy in developing countries, with about 500,000 new cases occurring in the world each year.
Other HPVs of particular interest with respect to cancer are types 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66 and 68 (referred to as “oncogenic-HPV types”). Types 16 and 18 are those which have the highest association with cervical cancer. Types 31 and 45 are the types with the next highest association with a cancer risk (Munoz N, Bosch FX, de Sanjose S et al. International Agency for Research on Cancer Multicenter Cervical Cancer Study Group. N Engl J Med 2003; 348: 518-27.)
HPV virus like particles (VLPs) have been suggested as potential vaccines for treatment of HPV. Animal studies have shown that VLPs produce no cross protection against infection for other HPV types—see, for example Suzich, J. A., et al, Proc Natl Acad Sci, 92: 11553-11557, 1995, and Breitburd, Seminars in Cancer Biology, vol 9, 1999, pp 431-445.
WO2004/056389 discloses that an HPV 16, 18 VLP vaccine can provide cross protection against infection by HPV types other than 16 and 18. Statistically significant protection was observed against certain groups of HPV types. However, the level of cross protection against individual types within groups was not disclosed.
There is still a need for a vaccine that protects against multiple HPV types.